Examples of electronically controlled cartridge control valves for fuel injectors are shown in U.S. Pat. No. 5,494,219 to Maley et al., U.S. Pat. No. 5,407,131 to Maley et al., U.S. Pat. No. 4,869,462 to Logie et al., and U.S. Pat. No. 4,717,118 to Potter. In each of these examples, the injector includes a mechanically actuated fuel pumping plunger and an electronically actuated fuel pressure control valve assembly. The pressure control valve assembly includes a solenoid operated poppet valve member that controls fuel pressure in the injector in order to control fuel injection delivery and timing. Fuel pressure is controllably enabled to be developed within the injector by electrical actuation of the pressure control valve assembly. Fuel pressure is controllably prevented from developing within the injector by not electrically actuating the pressure control valve so that fuel can spill through a return passage while the plunger is undergoing a portion of its downward pumping stroke.
In such electronically controlled fuel injectors, the armature of the pressure control valve assembly moves the poppet valve member in one direction until it engages a valve seat, and holds the poppet valve in its closed position to enable fuel pressure to be developed in the injector, eventually resulting in fuel injection. At the end of the fuel injection cycle, the solenoid is de-energized, and a return spring moves the poppet valve member off the valve seat, returning the poppet valve member to its open position, which relieves fuel pressure by spilling the fuel back to a fuel reservoir.
Because of manufacturing and cost constraints, the valve must typically include several valve body components joined to one another. In most cases, a sealing land defining the contact area between two valve body components must withstand cyclic high fuel pressures without leaking. These pressures typically vary on the order from about 0 psi to 20,000 psi, or more, many times per second, and the sealing land must reliably seal against leakage over many hundreds of millions of injection pressure cycles. Because of the large number of cycles involved and the relatively high pressures, conventional o-ring and/or gasket sealing techniques are incapable of reliably sealing against leakage in this extreme environment. In other words, engineers must typically rely upon a metal to metal sealing land to adequately and reliably prevent leakage in some high pressure areas within control valves for fuel injectors.
Although machining technology is sufficiently developed to allow adequate high pressure sealing between two planar surfaces of a pair of metal valve body components, the ability to provide an adequate force to hold the two valve body components together sufficiently to prevent leakage is somewhat more problematic. In the case of cartridge control valves for fuel injectors, this force is often produced by relying upon a relatively high torque when attaching the control valve to an injector body. High torques can lead to excessive stress on the metal parts and cause distortion of the matched clearance bores. This in turn can cause parts to break and/or the distortion can cause a seizure of moving components within the fuel injector. Any improvement that reduces the amount of force necessary to hold two metallic valve body components together is desirable because of the decreased sensitivity to reliance upon high joining forces.
The present invention is directed to overcoming one or more of the problems as set forth above.